Removable flash memory storage cards such as Multi Media Card (MMC) and Secure Digital (SD) cards are increasingly being used in portable devices to obtain more storage for digital data, such as programs and content. Electronic devices such as smart cell phones, multimedia phones, personal digital assistants (PDAs), MP3 players, digital still cameras and digital video recorders provide build-in slots for insertion of removable memory storage cards such as MMCmobile, MMCmicro, miniSD and microSD cards. These reduced-size form factor cards are preferred because a typical portable device must be lightweight and small in size to fit in a user's hand. Due to very tight spacing, the slot available inside a device typically is designed to use the smallest card available in the market. While this keeps the host device size small, the smallest form factor cards usually cannot provide as much memory density as the larger, standard size cards, and thus have less memory. Currently the smallest form factor cards in the market are the microSD and the MMCmicro cards that are about the size of a fingernail.
Although these miniaturized cards can allow a small and thin portable electronic device to use a small space for the insertion slot, the cards themselves are limited in the amount of flash memory they can carry. Currently, for instance, the maximum capacity of a standard MMC card is 4 gigabytes (GB); for the miniaturized MMCmicro, the maximum capacity is only 512 megabytes (MB) or 1 GB. Similarly, the capacity of the microSD card currently is 1 GB, compared to 2 GB for standard size SD cards. Although nonvolatile flash memory semiconductor IC chips will continue to increase in memory capacity as the transistor process parameters shrink in size (die-shrink) and hence offers more memory capacity per unit die area, the miniaturized micro memory cards will always lag behind their larger sibling cards in total capacity, due to the physical limit in size and thickness. The number of IC chips and sizes that can fit inside small cards are limited compared to the larger cards.
After a removable card has been inserted into a portable device slot, the card capacity defines the amount of memory capacity the portable device can utilize, in addition to any built-in memories of the device. For example, if a 256 MB card is inserted into a card slot of a cell phone, the phone has the capacity of 256 MB (in addition to the phone's internal memory). This memory capacity is not expandable or scalable, unless the card is replaced with another card having a higher capacity, say, 512 MB. If a user wishes to have even higher capacity, he or she will have to wait for the card manufacturers to provide a new reduced-size card having higher memory capacity.
Accordingly, what is needed is the ability to expand the memory capacity of electronic portable devices using reduced sized memory cards without having to replace such memory cards with higher capacity cards, and without affecting the portability of the devices. The present invention addresses such a need.